The present embodiments relate to a method and an apparatus for monitoring an irradiation system.
Methods and apparatus for monitoring an irradiation system may be used, for example, prior to a planned irradiation for evaluating whether the system is functioning correctly.
Particle therapy is an established method for treating tissue (e.g., for treating tumor diseases). However, irradiation methods of the kind used in particle therapy are also used in nontherapeutic fields. Examples include research work (e.g., for product development), in the context of particle therapy done on non-living phantoms or bodies, and the irradiation of materials.
In such fields, charged particles such as protons or carbon ions or other ions are accelerated to high energy levels, shaped into a particle beam, and guided to one or more irradiation chambers via a high-energy beam transportation system. In the irradiation chamber, the target volume to be irradiated is irradiated with the particle beam.
It may happen that the target volume to be irradiated moves. For example, when a patient is being irradiated, a respiratory motion may cause the tumor that is to be irradiated to move.
One known way of compensating for the motion of the target volume is irradiation methods that are known by the terms “rescanning,” “gating,” and “tracking.” “Rescanning” may be that the beam is applied as planned multiple times, so that incorrect doses in the individual scans are averaged. “Gating” may be that the beam is applied only within fixed time slots of the motion, so that the influence of the motion is lessened or even excluded entirely. “Tracking” may be that the beam, with which the target volume is being irradiated, tracks the motion of the target volume. If the beam is a particle beam, this may be attained, for example, by deflecting the beam using magnet systems, such that a course of the motion of the target volume is tracked. Optionally, the beam may also be varied in energy to adapt the penetration depth of the beam to the motion of the target volume. Tracking may also be done in irradiation with photons. This may be done, for example, by modifying the collimator that limits the beam, the collimator opening being adapted to the motion of the target volume.
Methods and apparatuses, with which motion tracking of the beam may be achieved, are known from U.S. Pat. No. 6,891,177 B1 and U.S. Pat. No. 6,710,362 B2, and US patent application 2006/0033042 A1.
These compensatory methods may be employed in the context of particle therapy in a scanning process, in which a plurality of spatially narrow irradiation doses are deposited successively at various sites in the target volume. In other words, these compensatory methods may be employed in the context of particle therapy in a scanning process, in which the particle beam sweeps in a scanning fashion over the target volume.